This invention relates generally to pipeline corrosion detecting devices for measurement of the corrosive effect of fluid whether gas or liquid carried in the pipeline. More particularly, the invention relates to test coupon holders for inserting and retrieving coupons from large diameter pipelines to periodically check for corrosion and wear of the pipeline due to flow of a medium such as corrosive fluids or suspensions through the pipeline.
It has become customary to determine the corrosiveness of a pipeline fluid in order to estimate the extent of corrosion to the interior surfaces of the pipeline by inserting into the flowing fluid a coupon of metal of standardized size, shape, composition and finish. By visual inspection or by measuring the loss of weight for a selected period of immersion in the fluid, the rate of corrosion can be determined. Frequently the coupons are inserted into the pipeline while the line is shut down by removing a plug from the pipeline, inserting the coupon and then replacing the plug so as to seal the line against leakage.
It is known that the flow of fluids or suspensions through pipelines can result in corrosion and deterioration of the pipeline at its inner wall. Such pipelines may often be inaccessible due to being buried under ground or otherwise concealed. Thus inserting test coupons constructed of a suitable material such as the material of the pipeline itself for establishing the corrosive effects on the coupon, the corrosive effects are in turn indicative of similar effects on the pipeline.
However, in many situations it is impractical to shut down the pipeline and relieve the pressure within the pipeline each time it is desired to insert or remove a coupon. Thus, the prior art has developed devices by which test coupons may be inserted into the pipeline while the fluid flowing through the line is under pressure within the line. The coupon so positioned may remain within the line for predetermined periods of time and then be removed from the line without interrupting the fluid flow under pressure through the line.
A primary object of this invention is to provide a device for inserting into and retrieving a corrosion test coupon from the interior of a pipeline while the pipeline is operating with fluid flow under pressure.
It is another object of this invention to provide a device for positioning a corrosion test coupon inside a pipeline while the pipeline is under fluid pressure with complete safety to the operator of the device in inserting or retrieving the coupon.
It is a still further object of this invention to provide a test coupon holder having a coupon inserting rod provided with a safety stop element to prevent inadvertent withdrawal of the coupon inserting rod from the holder.
Another object of this invention is to provide a test coupon holder having a rod reciprocable in an elongated housing with the rod carrying the coupon and clamping means being provided in association with the housing to clamp the rod at desired locations to obtain proper positioning of the coupon within the pipeline being tested.